This invention relates to a drive mechanism for a reciprocating feed for a part, which drive mechanism includes a three-armed lever pivotably supported at a fixed point, one arm of this lever being in operative connection with the part to be fed, and the two other arms of this lever being arranged at an angle to each other and carrying rotatably mounted guide rollers which latter are in constant contact with drive disks rotatable together about a common axle.
A drive mechanism of this general type is described in German Unexamined Published Application (DOS) 2,153,991 which serves for the stepwise advancing of conveyor grippers which feed sheet-metal bands or strips to a press. In this German Application arrangement, an essential purpose to be fulfilled by the drive disks is to attain a course of motion of the conveyor grippers which has dwell intervals respectively at the two ends of a feeding step, during which dwell intervals other procedures, such as the opening and closing of the conveyor grippers, can be conducted.
This invention is based, at least in part, on the problem of making the advantages of the above-discussed type of drive mechanism, especially the positive drive transmission and the possibility of a practically no-play construction, available for the feed drive mechanism of a flying shear, and providing such a structure that the special kinematic conditions of the feed drive mechanism of a flying shear are taken into account.
The invention contemplates, in a drive mechanism of the type mentioned hereinabove, providing a construction such that the component to be advanced is a flying shear which executes during part of the feed path a movement in synchronism with the strip material to be severed, and that the effective radii of the drive disks vary constantly along the periphery so that, in the feeding direction, motion segments follow one another having an increasing, uniform, and decreasing velocity and, in the return stroke direction, motion segments follow one another having an increasing and a decreasing velocity.
A substantial advantage of the invention resides in that, while maintaining the positiveness of the drive transmission, it is possible in a simple manner, to obtain, in the feeding direction, a different speed curve along the feed path than in the return stroke direction. By the omission of a motion segment with a uniform speed in the return stroke direction, it is possible, for example, to limit the thus-occurring acceleration to a lower maximum value than in the feeding direction, whereby the existing forces of inertia can be reduced.
Preferred constructions of the drive mechanism of this invention, which are suitable for many purposes of application, provide that, in the feeding direction, respectively about 45.degree. of the rotary angle of the drive disks is associated with the increasing speed and with the decreasing speed, and approximately 90.degree. of the rotary angle of the drive disks is associated with the uniform speed and/or that, in the return stroke direction, respectively about 90.degree. of the rotary angle of the drive disks is associated with each of the increasing speed and the decreasing speed. A simple connection of the drive mechanism of this invention with the flying shear is established by coupling one arm of the three-armed lever with the shear via a connecting rod which is articulated at both its ends. The flying shear is guided, in this arrangement, along a path in parallel to the direction of motion of the strip material.
These and further objects, features and advantages of the present invention will become more obvious from the following description when taken in connection with the accompanying drawings, which show, for purposes of illustration only, a single embodiment in accordance with the present invention.